1. Field of the Invention
The present invention relates to a printing head for a dot printer.
2. Related Art And Prior Art Statement
A printing head for a general dot printer comprises a plurality of needles arranged in a retractable manner within a tubular needle holder, swingable armatures connected respectively to rearward ends of the respective needles, an armature stopper arranged rearwardly of the armatures for regulating backward positions of the respective armatures, springs for biasing respectively the armatures rearwardly, and solenoids provided correspondingly to the armatures. When any one of the solenoids is energized, the corresponding armature is attracted to move the needle forwardly. A forward end of the needle projects from the needle holder to perform printing. When energization of the solenoid is released, the armature is moved backwardly and impinges against the armature stopper. Noises are generated by an impact at the time the armature impinges against the armature stopper.
In view of the above, in order to solve the above-discussed problem, a printing head is disclosed in Japanese Patent Laid-Open No. 62843/1991 in which a resilient or elastic element is provided for being abutted against rearward ends of respective wires to absorb the impact. However, the printing head is such that, when the wires are repeatedly abutted, the elastic element is abraded or worn off by the impact, and the wires are cut into the elastic element so that the printing head is difficult to operate normally when the wires are again released from the elastic element.
Further, an impact dot head is disclosed in Japanese Patent Laid-Open No. 231765/1987 in which a metallic spacer and a rubber spacer which are polymerized to each other are arranged as a buffer material on lever abutting portions.
The above-described impact dot head has the following problems. That is, it is possible to absorb the impact by the rubber spacer, and the metallic spacer is provided on the surface of the rubber spacer. Accordingly, there is no case where returned levers cut into the rubber spacer. Printing can normally be performed even after stoppage for a long period of time. The impact dot head is rich in durability. However, since the rubber spacer is provided on a rear surface of the metallic spacer, the number of parts increases. Not only this forms a primary factor of an increase in cost, but also it is difficult to produce thickness accuracy of the rubber space. Thus, if the accuracy of this portion is poor, variation is apt to occur in printing performance.